He is mentioned only once in medieval Welsh prose, in "Culhwch ac Olwen," but is mentioned more frequently in the poetry of Taliesin, particularly in both the long, Llyfr Taliesin versoin of "Cad Goddeu", and the brief version, which tells of his battle with the otherworld forces of Arawn and Bran; he is helped by his uncle Math fab Mathonwy and his brother Gwydion.

With Gwydion and Gofannon, he forms a triad that can possibly represent the tripartite division of European society: Gwydion the wizard, Gofannon the smith, and Amaethon the plowman.